Image sensor including color filter isolation layer and method of manufacturing the same

ABSTRACT

An image sensor including a color filter isolation layer and a method of manufacturing the image sensor. The image sensor includes a plurality of color filters that transmit light of a predetermined wavelength band to a light sensing layer. The image sensor also includes an isolation layer disposed between adjacent ones of the plurality of color filters. The isolation layer is formed of a material having a lower refractive index than a refractive index of the color filters, thus totally internally reflecting light incident on the isolation layer from one of the plurality of color filters.

RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 14/828,869 filed onAug. 18, 2015, which claims priority from Korean Patent Application No.10-2014-0106964, filed on Aug. 18, 2014, in the Korean IntellectualProperty Office, the disclosures of which are incorporated herein intheir entirety by reference.

BACKGROUND 1. Field

Apparatuses and methods consistent with exemplary embodiments relate toimage sensors and methods of manufacturing the same, and moreparticularly, to image sensors including a color filter isolation layercapable of preventing crosstalk and loss of light in a peripheralportion of the image sensors and methods of manufacturing the imagesensors.

2. Description of the Related Art

Typically, color displays and color image sensors display multicolorimages and detect colors of light incident thereon using color filters.Many color displays or color image sensors include an array of a redcolor filter that transmits only red light, a green color filter thattransmits only green light, and a blue color filter that transmits onlyblue light. Accordingly, a red pixel at which a red color filter isdisposed may display or sense only red light, a green pixel at which agreen color filter is disposed may display or sense only green light,and a blue pixel at which a blue color filter is disposed may display orsense only blue light. In such a structure, a predetermined color may berepresented by adjusting the relative amounts of light output by thered, green, and blue pixels, or a color of incident light may bedetermined by sensing light incident on the red, green, and blue pixels.In addition to an RGB color filter scheme, a CYGM color filter scheme inwhich complementary cyan, yellow, green, and magenta color filters aredisposed at four respective pixels is used.

An image capturing device may include an objective lens and a colorimage sensor. The objective lens focuses light incident from the outsideonto a color image sensor, and the color image sensor may form an imageby sensing the focused light. However, while light incident on pixels ina center portion of the color image sensor, located around an opticalaxis of the objective lens, is incident at an almost normal angle lightincident on pixels at edges of the color image sensor, which are awayfrom the optical axis, is incident at an oblique angle. Varioustechniques have been suggested in order to form a more exact image,taking into consideration this variation of the incidence angle.

SUMMARY

According to an aspect of an exemplary embodiment, an image sensorincludes: a light sensing layer sensing incident light to generate anelectrical signal; a color filter layer arranged in a two-dimensionalarray on the light sensing layer, the color filter layer including aplurality of color filters that transmit light of a predeterminedwavelength band to the light sensing layer; and an isolation layerdisposed between adjacent ones of the plurality of color filters andformed of a material having a lower refractive index than a refractiveindex of the plurality of color filters, wherein the isolation layer isinterposed between at least one color filter and the light sensing layeror extends to cover a light incident surface of at least one colorfilter.

The isolation layer may be configured such that a total reflectioncritical angle at an interface between the color filters and theisolation layer is greater than 45 degrees.

The plurality of color filters may include: a first color filtertransmitting light of a first wavelength band; a second color filtertransmitting light of a second wavelength band; and a third color filtertransmitting light of a third wavelength band, wherein the isolationlayer extends among the first through third color filters, on a lightincident surface of at least one of the first through third colorfilters, and between at least one of the first through third colorfilters and the light sensing layer.

The isolation layer may extend on a light incident surface of the firstcolor filter, and between the second color filter and the light sensinglayer, and a thickness of the second color filter may be smaller than athickness of the first color filter.

The isolation layer may further extend between the third color filterand the light sensing layer, a thickness of the third color filter maybe smaller than a thickness of the first color filter, and distancesbetween the light incident surfaces of the first through third colorfilters and the light sensing layer may be the same as each other.

The image sensor may further include: a color separation elementdisposed opposite the first color filter and configured to transmitlight of the first wavelength band to the first color filter, and torefract or diffract light of the second wavelength band toward thesecond color filter, and to refract or diffract light of the thirdwavelength band toward the third color filter.

The image sensor may further include a transparent dielectric layerdisposed on the color filter layer, and the color separation element maybe fixed and buried within the transparent dielectric layer.

The image sensor may further include a color separation element that isdisposed opposite the first color filter and configured to transmitlight of the first wavelength band to the first color filter and torefract or diffract light in the second and third wavelength bandstoward the second and third color filters.

The color filter layer may include: a first row in which a plurality offirst color filters that transmit light of a first wavelength band and aplurality of second color filters that transmit light of a secondwavelength band are alternately arranged in a first direction; and asecond row in which a plurality of first color filters that transmitlight of a first wavelength band and a plurality of third color filtersthat transmit light of a third wavelength band are alternately arrangedin the first direction, and the first row and the second row may bealternately arranged in a second direction perpendicular to the firstdirection.

The image sensor may further include: a first color separation elementdisposed opposite the first color filter of the first row and configuredto transmit light of the first wavelength band to the first color filterand to refract or diffract light of the second wavelength band to thesecond color filter; and a second color separation element disposedopposite the first color filter of the second row and configured totransmit light of the first wavelength band to the first color filterand to refract or diffract light of the third wavelength band to thethird color filter.

The image sensor may further include a transparent dielectric layerdisposed on the color filter layer, and the first and second colorseparation elements may be fixed and buried within the transparentdielectric layer.

The image sensor may further include a color separation element that isdisposed opposite the first color filter of the first row and the secondrow and configured to transmit light of the first wavelength band to thefirst color filter and to refract or diffract light in the second andthird wavelength bands to the second or third color filter.

The isolation layer may extend on a light incident surface of the firstcolor filter, between the first color filter and the second colorfilter, and between the second color filter and the light sensing layerin the first row, and the isolation layer may extend on a light incidentsurface of the first color filter, between the first color filter andthe third color filter, and between the third color filter and the lightsensing layer in the second row.

Thicknesses of the second and third color filters may be smaller than athickness of the first color filter, and respective distances betweenlight incident surfaces of the first through third color filters and thelight sensing layer may be the same.

A distance between bottom surfaces of the second and third color filtersand the light sensing layer may be greater than a distance between abottom surface of the first color filter and the light sensing layer,and a distance between light incident surfaces of the second and thirdcolor filters and the light sensing layer may be greater than a distancebetween a light incident surface of the first color filter and the lightsensing layer.

Side surfaces of the first through third color filters may be inclined.

An internal angle between the bottom surface and the side surface of thefirst color filter may be smaller than 90 degrees, and an internal anglebetween the bottom surface and the side surface of the second colorfilter may be greater than 90 degrees.

An area of the light incident surface of the second color filter may begreater than an area of the light incident surface of the first colorfilter.

An internal angle between the bottom surface and the side surface of thefirst color filter may be greater than 90 degrees, and an internal anglebetween the bottom surface and the side surface of the second colorfilter may be smaller than 90 degrees.

The isolation layer may extend on a light incident surface of the secondcolor filter, between the second color filter and the first colorfilter, and between the first color filter and the light sensing layerin the first row.

Also, the isolation layer may extend on a light incident surface of thethird color filter, between the first color filter and the third colorfilter, and between the first color filter and the light sensing layerin the second row.

According to an aspect of another exemplary embodiment, an imagecapturing apparatus including the above-described image sensor isincluded.

According to an aspect of another exemplary embodiment, a method ofmanufacturing an image sensor, includes: providing a light sensing layerthat senses incident light to generate an electrical signal; forming aplurality of first color filters transmitting light of a firstwavelength, on the light sensing layer at predetermined distances;forming an isolation layer to cover an upper surface of the lightsensing layer and side surfaces and light incident surfaces of theplurality of first color filters; and forming a plurality of secondcolor filters transmitting light of a second wavelength band, on theisolation layer between the plurality of first color filters, atpredetermined distances, wherein the isolation layer is formed of amaterial having a lower refractive index than refractive indices of thefirst and second color filters, and the isolation layer extends on alight incident surface of the first color filter layer and between thesecond color filter layer and the light sensing layer.

A thickness of the second color filters may be smaller than a thicknessof the first color filters, and respective distances between lightincident surfaces of the first and second color filters and the lightsensing layer may be the same.

A distance between a bottom surface of the second color filter and thelight sensing layer may be greater than a distance between a bottomsurface of the first color filter and the light sensing layer, and adistance between a light incident surface of the second color filter andthe light sensing layer may be greater than a distance between a lightincident surface of the first color filter and the light sensing layer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other exemplary aspects and advantages will become apparentand more readily appreciated from the following description of exemplaryembodiments, taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a schematic cross-sectional view of a structure of an imagesensor according to an exemplary embodiment;

FIG. 2 is a schematic cross-sectional view of a structure of an imagesensor according to another exemplary embodiment;

FIG. 3 is a schematic plan view of a pixel structure of an image sensoraccording to another exemplary embodiment;

FIG. 4A is a cross-sectional view of a first pixel row of the imagesensor of FIG. 3 cut along a line A-A′;

FIG. 4B is a cross-sectional view of a second pixel row of the imagesensor of FIG. 3 cut along a line B-B′;

FIGS. 5A through 5C are cross-sectional views illustrating manufacturingprocesses of the image sensor illustrated in FIG. 3 according to anexemplary embodiment;

FIGS. 6A and 6B are respectively schematic cross-sectional views ofstructures of a first pixel row and a second pixel row of an imagesensor according to another exemplary embodiment;

FIG. 7 is a schematic cross-sectional view of a structure of an imagesensor according to another exemplary embodiment;

FIGS. 8A and 8B are respectively schematic cross-sectional views ofstructures of a first pixel row and a second pixel row of an imagesensor according to another exemplary embodiment;

FIG. 9 is a graph exemplarily showing a spectrum distribution of lightabsorbed by light sensing cells of the image sensor illustrated in FIGS.8A and 8B; and

FIG. 10 is a graph exemplarily showing a spectrum distribution of lightabsorbed by light sensing cells of an image sensor according to acomparative example.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments which areillustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, theexemplary embodiments may have different forms and should not beconstrued as being limited to the descriptions set forth herein.Accordingly, exemplary embodiments are merely described below, byreferring to the figures, to explain aspects of the present description.

Hereinafter, an image sensor including a color filter isolation layerand a method of manufacturing the image sensor will be described indetail with reference to the accompanying drawings. In the drawings,like reference numbers refer to like elements, and also the size of eachelement may be exaggerated for clarity of illustration. Embodimentsdescribed herein are for illustrative purposes only, and variousmodifications may be made therefrom. In the following description, whenan element is referred to as being “above” or “on” another element in alayered structure, it may be directly on the other element while makingcontact with the other element or may be above the other element withoutmaking contact with the other element.

FIG. 1 is a schematic cross-sectional view of a structure of an imagesensor 100 according to an exemplary embodiment. Referring to FIG. 1,the image sensor 100 may include a light sensing layer 10 that sensesincident light and thereby generates an electrical signal; a colorfilter layer 20 that is disposed on the light sensing layer 10 andcomprises a plurality of color filters 20R, 20G, and 20B, each of whichtransmits light of only a desired wavelength band and provides the lightsensing layer 10 with the transmitted light; and an isolation layer 21disposed between adjacent color filters of the color filters 20R, 20G,and 20B.

The light sensing layer 10 may be divided into a plurality of lightsensing cells 10R, 10G, and 10B. For example, the plurality of lightsensing cells 10R, 10G, and 10B may include a red light sensing cell10R, a green light sensing cell 10G, and a blue light sensing cell 10B.Although one red light sensing cell 10R, one green light sensing cell10G, and one blue light sensing cell 10B are illustrated in FIG. 1 forconvenience, in practice, there may be a plurality of red light sensingcells 10R, green light sensing cells 10G, and blue light sensing cells10B, which may be arranged in a two-dimensional (2D) array. The lightsensing cells 10R, 10G, and 10B may each independently convert anintensity of incident light into an electrical signal. For example, anelectrical signal generated in the red light sensing cell 10R may dependon an intensity of light incident on only the red light sensing cell 10Ritself, regardless of the intensities of light incident on otheradjacent light sensing cells 10G and 10B. The light sensing layer 10 maybe formed of, for example, a charge-coupled device (CCD) or acomplementary metal oxide semiconductor (CMOS).

The color filters 20R, 20G, and 20B may be respectively disposed on thelight sensing cells 10R, 10G, and 10B that respectively correspond tocolor filters 20R, 20G, and 20B. For example, the plurality of colorfilters 20R, 20G, 20B may include a red color filter 20R that transmitslight in a red wavelength band, a green color filter 20G that transmitslight in a green wavelength band, and a blue color filter 20B thattransmits light in a blue wavelength band. Although one red color filter20R, one green color filter 20G, and one blue color filter 20B areillustrated in FIG. 1 for convenience, in practice, there may be aplurality of red color filters 20R, green color filters 20G, and bluecolor filters 20B which may be arranged on the light sensing layer 10 ina two-dimensional array.

Although the red color filter 20R, the green color filter 20G, and theblue color filter 20B are arranged in this order in FIG. 1, the order ismerely exemplary and the arrangement of the color filters is not limitedthereto. Furthermore, the red color filter 20R, the green color filter20G, and the blue color filter 20B, of the color filter layer 20according to the present embodiment, are also exemplary, and the colorfilter layer 20 may also include color filters of other colors. Forexample, the color filter layer 20 may include cyan, yellow, green, andmagenta color filters. Alternatively, filters which transmit otherwavelength bands, including an infrared wavelength band, or anultraviolet wavelength band, may be used. Thus, thespecifically-described colors and arrangement orders of the colorfilters of the color filter layer 20 are merely exemplary forconvenience of description.

The isolation layer 21 is disposed between adjacent color filters,thereby optically separating each adjacent pair of the color filters. Tothis end, the isolation layer 21 may be formed of a material having alower refractive index than that of the plurality of color filters 20R,20G, and 20B. For example, the isolation layer 21 may be formed of amaterial such as a polymethylmetacrylate (PMMA), a silicon acrylate,cellulose acetate butyrate (CAB), a silicon oxide (SiO2), or afluoro-silicon acrylate (FSA). As long as the refractive index of theisolation layer is lower than that of the adjacent color filters, theisolation layer 21 may be formed of any material. In particular, theisolation layer 21 may be formed using a physical vapor deposition (PVD)method or a chemical vapor deposition (CVD) method used in typicalsemiconductor processes.

The isolation layer 21 totally internally reflects light that isobliquely incident through light incident surfaces of the respectivecolor filters 20R, 20G, and 20B and which exits through side surfaces ofthe respective color filters 20R, 20G, and 20B, thereby opticallyseparating each of the color filters 20R, 20G, and 20B from otheradjacent color filters 20R, 20G, and 20B. For example, as illustrated inFIG. 1, light L that is incident obliquely on a point P1 on a lightincident surface of the green color filter 20G may reach a point P2 on aside surface of the green color filter 20G. The side surface of thegreen color filter 20G is an interface with the isolation layer 21 whichhas a lower refractive index than the green color filter 20G. Thus, thelight L will be totally internally reflected at the point P2 so as toreturn to the inside of the green color filter 20G. Thereafter, thelight L is incident on the green light sensing cell 10G to contribute tothe signal output by the green light sensing cell 10G.

If the isolation layer 21 were not included, the light L would beincident on the blue color filter 20G that is adjacent to the greencolor filter 20G as denoted by a dotted arrow in FIG. 1. Then the lightL would be incident on the blue light sensing cell 10B and wouldcontribute to the signal output by the blue light sensing cell 10B.Consequently, there would be a loss of light in the green light sensingcell 10G, and excessive light incident on the blue light sensing cell10B, resulting the image formed by the image sensor 100 being formedwith inaccurate color information.

Thus, the image sensor 100 of the present embodiment may prevent suchloss of light and crosstalk by using the isolation layer 21.Consequently, the light utilization efficiency may be improved andcolors may be accurately sensed. In particular, with an image capturingdevice including the image sensor 100, accurate color information can beobtained even from edge areas of the image sensor 100 on which light isobliquely incident.

FIG. 2 is a schematic cross-sectional view of a structure of an imagesensor 110 according to another exemplary embodiment. Referring to FIG.2, the isolation layer 21 is disposed between adjacent color filters ofthe plurality of color filters 20R, 20G, and 20B, and may also beinterposed between one or more of the color filters 20R, 20G, and 20Band the light sensing layer 10 or may extend to cover one or more lightincident surfaces of the color filters 20R, 20G, and 20B. For example,the isolation layer 21 may extend between the red color filter 20R andthe light sensing layer 10, may extend over the light incident surfaceof the green color filter 20G, and may extend between the blue colorfilter 20B and the light sensing layer 10. Heights of the red colorfilter 20R, the green color filter 20G, and the blue color filter 20Bmay be the same. That is, distances between the light incident surfacesof each of the red color filter 20R, the green color filter 20G, and theblue color filter 20B and the light sensing layer 10 may be the same aseach other.

According to the embodiment illustrated in FIG. 2, due to the isolationlayer 21 formed on the light sensing layer 10, thicknesses of the redcolor filter 20R and the blue color filter 20B may be smaller than athickness of the green color filter 20B by an amount equal to athickness of the isolation layer 21 on the light sensing layer 10. Thus,by adjusting the thickness of the isolation layer 21 on the lightsensing layer 10, the thicknesses of the red color filter 20R and theblue color filter 20B may be easily adjusted. By adjusting thethicknesses of the red color filter 20R and the blue color filter 20B,color spectrum characteristics of the image sensor 110 may becontrolled. That is, color characteristics of images obtained by usingthe image sensor 110 may be adjusted without image signal processingwhich requires complicated calculation and a long time.

Although the isolation layer 21 is disposed on bottom surfaces of thered color filter 20R and the blue color filter 20B and on the lightincident surface of the green color filter 20G in FIG. 2, arrangement ofthe isolation layer 21 is not limited thereto. Also, although theisolation layer 21 is alternately disposed on bottom surfaces and alight incident surface of the color filters 20R, 20G, and 20B,arrangement of the isolation layer 21 is not limited thereto. Thearrangement and the thickness of the isolation layer 21 may varyaccording to desired color spectrums of the image sensor 110.

The bottom surfaces of the red and blue color filters 20R and 20Bcontact the isolation layer 21 which has a relatively low refractiveindex, and thus, light that is totally internally reflected by the sidesurfaces of the red and blue color filters 20R and 20B may also betotally internally reflected by the bottom surfaces of the red and bluecolor filters 20R and 20B. In this case, since the light that is totallyinternally reflected by the bottom surfaces of the red and blue colorfilters 20R and 20B is not incident on the light sensing layer 10, lossof light may be caused. To prevent the loss of light, a difference inrefractive indices of the red and blue color filters 20R and 20B and arefractive index of the isolation layer 21 may be adjusted so as toprevent total internal reflection on the bottom surfaces of the red andblue color filters 20R and 20B.

For example, referring to FIG. 2, when an incident angle of lightincident on the side surface of the red color filter 20R is α, anincident angle of light that has been totally internally reflected bythe side surface of the red color filter 20R and is incident on thebottom surface of the red color filter 20R is α1=90°−α. Also, when atotal reflection critical angle between the red color filter 20R and theisolation layer 21 is α_(c), if light is incident on the side surface ofthe red color filter 20R at the total reflection critical angle α_(c),an incidence angle of that same light incident on the bottom surface ofthe red color filter 20R is 90°−α_(c). Here, if α1 is always smallerthan α_(c), total reflection does not occur on the bottom surface of thered color filter 20R. That is, since α1=90°−α_(c)<α_(c), 45°<α_(c).Accordingly, since a total reflection critical angle depends only on therefractive indices of two media, if a refractive index of the isolationlayer 21 is determined such that a total reflection critical angle isgreater than 45°, total reflection will not occur on the bottom surfacesof the red and blue color filters 20R and 20B.

FIG. 3 is a schematic plan view of a pixel structure of an image sensor120 according to another exemplary embodiment. Referring to FIG. 3, theimage sensor 120 may include a Bayer pattern in which two green colorfilters 20G are arranged in a first diagonal direction, and one bluecolor filter 20B and one red color filter 20R are arranged in a seconddiagonal direction that intersects the first diagonal direction. Theimage sensor 120 having a Bayer pattern may include a first pixel row120 a in which a plurality of blue color filters 20B and a plurality ofgreen color filters 20G are alternately arranged in a horizontaldirection and a second pixel row 120 b in which a plurality of greencolor filters 20G and a plurality of red color filters 20R arealternately arranged in a horizontal direction. Although only one firstpixel row 120 a and one second pixel row 120 b are illustrated in FIG. 3for convenience, a plurality of first pixel rows 120 a and a pluralityof second pixel rows 120 b may be alternately arranged in a verticaldirection. Also, the isolation layer 21 may be disposed around each ofthe blue color filters 20B, the green color filters 20G, and the redcolor filters 20R, as shown.

FIG. 4A is a cross-sectional view of the first pixel row 120 a of theimage sensor 120 of FIG. 3 cut along a line A-A′. Referring to FIG. 4A,a plurality of blue color filters 20B and a plurality of green colorfilters 20G are alternately arranged on the light sensing layer 10. Theblue color filters 20B and the green color filters 20G may berespectively disposed on corresponding blue light sensing cells 10B andcorresponding green light sensing cells 10G. The isolation layer 21 mayextend between the blue color filter 20B and the light sensing layer 10,between the blue color filter 20B and the green color filter 20G, and ona light incident surface of the green color filter 20G. That is, theisolation layer 21 may extend between adjacent color filters, along abottom surface of the blue color filter 20B, and along the lightincident surface of the green color filter 20G. Thus, a distance betweenthe bottom surface of the blue color filter 20B and the light sensinglayer 10 is greater than a distance between a bottom surface of thegreen color filter 20G and the light sensing layer 10. A height of thelight incident surface of the blue color filter 20B may be the same as aheight of the light incident surface of the green color filter 20G. Thatis, a distance between the light incident surface of the blue colorfilter 20B and the light sensing layer may be the same as a distancebetween the light incident surface of the green color filter 20G and thelight sensing layer 10. Accordingly, a thickness of the blue colorfilter 20B may be smaller than a thickness of the green color filter 20Gby an amount equal to a thickness of the isolation layer 21 on the lightsensing layer 10.

FIG. 4B is a cross-sectional view of the second pixel row 120 b of theimage sensor 120 of FIG. 3 cut along a line B-B′. Referring to FIG. 4B,a plurality of green color filters 20G and a plurality of red colorfilters 20R are alternately arranged on the light sensing layer 10. Thegreen color filters 20G and the red color filters 20R may berespectively disposed on corresponding green light sensing cells 10G andcorresponding red light sensing cells 10R. The isolation layer 21 mayextend between adjacent color filters, along a light incident surface ofthe green color filter 20G, and between the red color filter 20R and thelight sensing layer 10. Thus, a distance between the bottom surface ofthe red color filter 20R and the light sensing layer 10 is greater thana distance between a bottom surface of the green color filter 20G andthe light sensing layer 10. A distance between the light incidentsurface of the red color filter 20R and the light sensing layer 10 maybe the same as a distance between the light incident surface of thegreen color filter 20G and the light sensing layer 10. Accordingly, athickness of the red color filter 20R may be smaller than a thickness ofthe green color filter 20G by an amount equal to a thickness of theisolation layer 21 on the light sensing layer 10.

In FIGS. 4A and 4B, the thicknesses of the blue color filter 20B and thered color filter 20R may be the same or may be different, according todesired color characteristics for the image sensor 120. The thicknessesof the blue color filter 20B and the red color filter 20R may beadjusted based on a thickness of the isolation layer 21 on the lightsensing layer 10. For example, when a thickness of the blue color filter20B is greater than a thickness of the red color filter 20R, a thicknessof the isolation layer 21 between the blue color filter 20B and thelight sensing layer 10 may be smaller than a thickness of the isolationlayer 21 between the red color filter 20R and the light sensing layer10.

FIGS. 5A through 5C are cross-sectional views illustrating manufacturingprocesses of the image sensor 120 illustrated in FIG. 3 according to anexemplary embodiment. In detail, manufacturing processes of the firstpixel row 120 a of the image sensor 120 are illustrated.

First, referring to FIG. 5A, a light sensing layer 10 is provided. Thelight sensing layer is divided into a plurality of independent lightsensing cells 10B and 10G that sense incident light to generate anelectrical signal. Although a plurality of blue light sensing cells 10Band a plurality of green light sensing cells 10G are shown in FIG. 5Afor convenience, there is no substantial structural difference betweenthe blue light sensing cells 10B and the green light sensing cells 10G.For example, the light sensing layer 10 may be formed of acharge-coupled device (CCD) or a complementary metal oxide semiconductor(CMOS).

Also, a plurality of green color filters 20G that transmit only light ina green wavelength band may be formed on the light sensing layer 10. Asillustrated in FIG. 5A, a plurality of green color filters 20G may bedisposed on corresponding green light sensing cells 10G and may bespaced apart from one another by a predetermined distance. Although notillustrated, when forming the green color filters 20G in the first pixelrow 120 a, green color filters 20G of the second pixel row 120 b mayalso be formed at the same time. The green color filters 20G are formedbefore forming the blue color filters 20B, because the isolation layer21 is not interposed between the green color filters 20G and the lightsensing layer 10. According to another exemplary embodiment, when theisolation layer 21 is formed between the green color filters 20G and thelight sensing layer 10, and the isolation layer 21 is not presentbetween the blue color filters 20B and the light sensing layer 10, theblue color filters 20B may be formed before forming the green colorfilters 20G.

Next, referring to FIG. 5B, the isolation layer 21 may be formed tocover an upper surface of the light sensing layer 10 and side surfacesand light incident surfaces of the plurality of the green color filters20G. As described above, the isolation layer 21 may be formed of amaterial having a lower refractive index that of the green color filters20G or the blue color filters 20B. The isolation layer 21 may be formedby using, for example, a PVD method or a CVD method. As illustrated inFIG. 5B, the isolation layer 21 may have an overall uniform thickness.Alternatively, after forming the isolation layer 21, a thickness of theisolation layer 21 may be partially adjusted by using a chemicalmechanical polishing (CMP) method or by etching. For example, athickness of the isolation layer 21 on a light incident surface of thegreen color filter 20G may be adjusted, or a thickness of the isolationlayer 21 on the blue light sensing cell 10B and the red light sensingcell 10R may be adjusted.

Next, as illustrated in FIG. 5C, a plurality of blue color filters 20B,that transmit only light in a blue wavelength band, may be formed on theisolation layer 21 between the plurality of green color filters 20G. Theplurality of blue color filters 20B may be disposed on correspondingblue light sensing cells 10B, and may be arranged at predetermineddistances. Although not illustrated, after or before forming the bluecolor filters 20B in the first pixel row 120 a, red color filters 20Rmay be formed in the second pixel row 120 b.

FIGS. 6A and 6B are schematic cross-sectional views of structures of afirst pixel row 130 a and a second pixel row 130 b, respectively, of animage sensor according to another exemplary embodiment Like the firstpixel row 120 a of the image sensor 120 illustrated in FIG. 4A, thefirst pixel row 130 a illustrated in FIG. 6A includes a plurality ofblue color filters 20B and a plurality of green color filters 20G thatare alternately arranged. The isolation layer 21 may extend between theblue color filter 20B and the light sensing layer 10, between the bluecolor filter 20B and the green color filter 20G, and on a light incidentsurface of the green color filter 20G. Like the second pixel row 120 bof the image sensor 120 illustrated in FIG. 4B, the second pixel row 120b illustrated in FIG. 6B includes a plurality of green color filters 20Gand a plurality of red color filters 20R that are alternately arranged.The isolation layer 21 may extend on a light incident surface of thegreen color filter 20G, between the green color filter 20G and the redcolor filter 20R, and between the red color filter 20R and the lightsensing layer 10.

As illustrated in FIGS. 6A and 6B, the plurality of blue color filters20B, the plurality of green color filters 20G, and the plurality of redcolor filters 20R may have inclined side surfaces. For example, a firstinternal angle θ1 between a bottom surface and a side surface of thegreen color filter 20G may be smaller than 90 degrees, and a secondinternal angle θ2 between a bottom surface and a side surface of theblue color filter 20B or of the red color filter 20R may be greater than90 degrees. Thus, areas of the light incident surfaces of the blue colorfilter 20B and the red color filter 20R are greater than areas of thebottom surfaces thereof, and an area of the light incident surface ofthe green color filter 20G may be smaller than an area of a bottomsurface thereof. Also, an area of the light incident surface of thegreen color filter 20G may be smaller than areas of the light incidentsurfaces of the blue color filter 20B and the red color filter 20R.

However, the first and second internal angles θ1 and θ2 are not limitedto the embodiments illustrated in FIGS. 6A and 6B. According to desiredcolor spectrum characteristics of an image sensor, the first internalangle θ1 between the bottom surface and the side surface of the greencolor filter 20G and the second internal angle θ2 between the bottomsurface and the side surface of the blue color filter 20B or of the redcolor filter 20R may be adjusted appropriately. For example, the firstinternal angle θ1 may be greater than 90 degrees, and the secondinternal angle θ2 may be smaller than 90 degrees. Consequently, relativesizes of the light incident surfaces and the bottom surfaces of the bluecolor filter 20B and the red color filter 20R and relative sizes of thelight incident surface and the bottom surface of the green color filter20G may be adjusted. In this case, an area of the light incident surfaceof the green color filter 20G may be greater than areas of the lightincident surfaces of the blue color filter 20B and the red color filter20R.

Also, as illustrated in FIGS. 6A and 6B, heights of the light incidentsurfaces of the red color filter 20R, the green color filter 20G, andthe blue color filter 20B may be different. For example, a height of thelight incident surface of the red color filter 20R may be the same as aheight of the light incident surface of the blue color filter 20B, andmay be higher than a height of the light incident surface of the greencolor filter 20G. That is, a distance between the light incident surfaceof the red color filter 20R and the light sensing layer 10 and adistance between the light incident surface of the blue color filter 20Band the light sensing layer 10 may each be greater than a distancebetween the light incident surface of the green color filter 20G and thelight sensing layer 10. To this end, the light incident surfaces of thered color filter 20R and the blue color filter 20B may be formed at thesame height as an upper surface of the isolation layer 21 formed on thelight incident surface of the green color filter 20G. Also, a distancebetween the bottom surfaces of the red color filter 20R and the bluecolor filter 20B and the light sensing layer 10 may be greater than adistance between the bottom surface of the green color filter 20G andthe light sensing layer 10.

In the above-described structure, a step off between the light incidentsurface of the green color filter 20G and the light incident surface ofthe red color filter 20R and the blue color filter 20B and a thickness tof the isolation layer 21 between the red color filter 20R or the bluecolor filter 20B and the light sensing layer 10 may be adjusted tothereby adjust the thicknesses of the red color filter 20R and the bluecolor filter 20B. Thus, color spectrum characteristics of an imagesensor may be adjusted by appropriately selecting not only the first andsecond angles θ1 and θ2 described above but also the step off and thethickness t.

FIG. 7 is a schematic cross-sectional view of a structure of an imagesensor 140 according to another exemplary embodiment. Referring to FIG.7, the image sensor 140 may include a light sensing layer 10 that sensesincident light and thereby generates an electrical signal; a colorfilter layer 20 that is disposed on the light sensing layer 10 andcomprises a plurality of color filters 20R, 20G, and 20B; an isolationlayer 21 disposed between adjacent color filters of the plurality ofcolor filters 20R, 20G, and 20B; a transparent dielectric layer 25disposed on the color filter layer 20; and a color separation element 30that separates incident light according to wavelength, so that light ofdifferent wavelength bands proceeds along different paths. Each of thecolor filters 20R, 20G, and 20B transmits, to the light sensing layer10, light in only a desired wavelength band. The light sensing layer 10,the color filter layer 20, and the isolation layer 21 may have the samestructure and the same function as those of corresponding elementsdescribed above with reference to FIG. 2.

The color separation element 30 may separate light into colors bychanging a light proceeding path of light according to wavelength byusing diffraction or refraction. For example, various shapes, such as atransparent symmetrical or asymmetrical bar shape or a prism shapehaving an inclined surface, are known in the art as color separationelements 30. The color separation element 30 may be configured in any ofvarious manners according to a desired spectrum distribution of emittedlight. For example, as illustrated in FIG. 7, the color separationelement 30 may be disposed opposite the green color filter 20G. In thiscase, the color separation element 30 may be configured to transmitlight C2 in a green wavelength band to the green color filter 20G whichis directly below the color separation element 30; to refract ordiffract light C1 in a red wavelength band toward the red color filter20R on the left, and to refract or diffract light C3 in a bluewavelength band toward the blue color filter 20B on the right.Alternatively, the color separation element 30 may be configured totransmit light C2 in a green wavelength band to the green color filter20G, which is right below the color separation element 30, and torefract or diffract mixed light C1+C3, including light in both a redwavelength band and a blue wavelength band, toward the red and bluecolor filters 20R and 20B on the left and the right.

By using the color separation element 30, an amount of light that istransmitted through the respective color filters 20G, 20R, and 20Bincreases, and thus, a light utilization efficiency of an image sensormay be improved. Moreover, by using both the color separation element 30and the isolation layer 21, light separated by using the colorseparation element 30 may be used more efficiently. Light that isseparated by using the color separation element 30 and is incident onthe color filters 20G, 20R, and 20B proceeds approximately obliquely.The isolation layer 21 may totally internally reflect the light thatproceeds obliquely in the color filters 20G, 20R, and 20B to therebyprevent incidence of light on other adjacent light sensing cells 10R,10G, and 10B. Thus, a light utilization efficiency and color purity ofan image sensor and may be simultaneously improved.

The color separation element 30 may be buried in the transparentdielectric layer 25, such that it is in a fixed position. In order tosufficiently diffract and/or refract incident light, the colorseparation element 30 may be formed of a material having a higherrefractive index than that of the surrounding medium. That is, therefractive index of the color separation element 30 may be higher than arefractive index of the transparent dielectric layer 25. For example,the transparent dielectric layer 25 may be formed of SiO₂ orsiloxane-based spin on glass (SOG), and the color separation element 30may be formed of a high-refractive index material such as TiO₂, SiN₃,ZnS, ZnSe, or Si₃N₄. Specific shapes and materials of the colorseparation element 30 may be varied according to desired colorseparation characteristics.

FIGS. 8A and 8B are schematic cross-sectional views of structures of afirst pixel row 150 a and a second pixel row 150 b, respectively, of animage sensor according to another exemplary embodiment. The first pixelrow 150 a illustrated in FIG. 8A may include a light sensing layer 10; afirst color filter layer 20 a including a plurality of blue colorfilters 20B and a plurality of green color filters 20G that arealternately arranged on the light sensing layer 10; an isolation layer21 that extends between the blue color filter 20B and the light sensinglayer 10 and between the green color filter 20G and the blue colorfilter 20B and along a light incident surface of the green color filter20G; a transparent dielectric layer 25 disposed on the first colorfilter layer 20 a; and a first color separation element 31 a thatseparates incident light according to wavelength and allows light ofdifferent wavelength bands to proceed along different paths. The lightsensing layer 10, the first color filter layer 20 a, and the isolationlayer 21 may have the same structure and the same function as those ofcorresponding elements described above with reference to FIG. 4A.

Also, the first pixel row 150 b illustrated in FIG. 8B may include alight sensing layer 10; a second color filter layer 20 b including aplurality of red color filters 20R and a plurality of green colorfilters 20G that are alternately arranged on the light sensing layer 10;an isolation layer 21 that extends between the red color filter 20R andthe light sensing layer 10, between the green color filter 20G and thered color filter 20R, and along a light incident surface of the greencolor filter 20G; a transparent dielectric layer 25 disposed on thesecond color filter layer 20 b; and a second color separation element 31b that separates incident light according to wavelength and allows lightof different wavelength bands to proceed along different paths. Thelight sensing layer 10, the second color filter layer 20 b, and theisolation layer 21 may have the same structure and the same function asthose of corresponding elements described above with reference to FIG.4B.

As illustrated in FIGS. 8A and 8B, the first color separation element 31a and the second color separation element 31 b may be buried in thetransparent dielectric layer 25, such that they are in fixed positions.Also, the first color separation element 31 a may be disposed oppositethe green color filter 20G of the first pixel row 150 a, and the secondcolor separation element 31 b may be disposed opposite the green colorfilter 20G of the second pixel row 150 b, as shown. In theabove-described structure, the first color separation element 31 a maybe configured to transmit light C2 of a green wavelength band to thegreen color filter 20G, which is right below the first color separationelement 31 a, and to refract or diffract light C3 of a blue wavelengthband toward the blue color filters 20B on the left and the right. Also,the second color separation element 31 b may be configured to transmitlight C2 of a green wavelength band to the green color filter 20G, whichis right below the second color separation element 31 b, and to reflector diffract light C1 of a red wavelength band toward the red colorfilters 20R on the left and the right.

Alternatively, the first color separation element 31 a and the secondcolor separation element 31 b may be configured to have the samefunction. In this case, the first and second color separation elements31 a and 31 b may be configured to transmit light C2 of a greenwavelength band to the green color filter 20G, which is right below thefirst and second color separation elements 31 a and 31 b, and to reflector diffract mixed light C1+C3, including light in both a red wavelengthband and a blue wavelength band, toward the blue color filters 20B orthe red color filters 20R that are respectively disposed on the left orthe right. Also, the transparent dielectric layer 25 and the first andsecond color separation elements 31 a and 31 b illustrated in FIGS. 8Aand 8B may also be applied to the image sensors 130 a and 130 billustrated in FIGS. 6A and 6B.

FIG. 9 is a graph showing an exemplary spectrum distribution of lightabsorbed by the light sensing cells 10R, 10G, and 10B of the imagesensors 150 a and 150 b illustrated in FIGS. 8A and 8B. In FIG. 9, ‘Bfilter’, ‘G filter,’ and ‘R filter’ respectively denote spectrumdistributions of light that are incident on the blue, green, and redlight sensing cells 10B, 10G, and 10R when the first and second colorseparation elements 31 a and 31 b are not used. Also, in FIG. 9, ‘R’ and‘B’ respectively denote spectrum distributions of light incident on thered and blue light sensing cells 10R and 10B when the first and secondcolor separation elements 31 a and 31 b are used, and ‘Gb’ and ‘Gr’respectively denote spectrum distributions of light incident on thegreen light sensing cell 10G of the first pixel row 150 a and the greenlight sensing cell 10G of the second pixel row 150 b when the first andsecond color separation elements 31 a and 31 b are used. As can be seenfrom the graph of FIG. 9, by using the first and second color separationelements 31 a and 31 b, a light utilization efficiency may be improvedas compared to when just the color filters 20G, 20R, and 20B are used.

FIG. 10 is a graph showing an exemplary spectrum distribution of lightabsorbed by light sensing cells 10R, 10G, and 10B of an image sensoraccording to a comparative example. The image sensor according to thecomparative example has almost the same structure as the image sensors150 a and 150 b illustrated in FIGS. 8A and 8B except that the isolationlayer 21 is not included. That is, in the image sensor according to thecomparative example, the color filters 20G, 20R, and 20B and the firstand second color separation elements 31 a and 31 b are included but theisolation layer 21 is not disposed between the color filters 20G, 20R,and 20B. Referring to the graph of FIG. 10, a light utilizationefficiency of the image sensor according to the comparative example isrelatively high compared to when just the color filters 20G, 20R, and20B are used. However, the light utilization efficiency of the imagesensor according to the comparative example is lower than the lightutilization efficiency of the image sensor according to the presentexemplary embodiment which further includes the isolation layer 21.Accordingly, the light utilization efficiency may be remarkablyincreased by using both the isolation layer 21 and the first and secondcolor separation elements 31 a and 31 b as in the present exemplaryembodiment.

It should be understood that the exemplary embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

While one or more exemplary embodiments have been described withreference to the figures, it will be understood by those of ordinaryskill in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the presentinvention as defined by the following claims.

What is claimed is:
 1. An image sensor comprising: a light sensing layerconfigured to generate an electrical signal using incident light; acolor filter layer disposed on the light sensing layer, wherein thecolor filter layer comprises a first color filter configured to transmitlight in a first wavelength band and a second color filter configured totransmit light in a second wavelength band, different from the firstwavelength band; and an isolation layer disposed between the first colorfilter and the second color filter, wherein a refractive index of theisolation layer is lower than a refractive index of any one of the firstcolor filter and the second color filter, wherein the isolation layer isfurther disposed on a light incident surface of the first color filterand between the second color filter and the light sensing layer, whereinthe isolation layer is not disposed between the first color filter andthe light sensing layer, and is not disposed on the light incidentsurface of the second color filter, and wherein a surface level of alight incident surface of the second color filter is identical to asurface level of the light incident surface of the first color filter.2. The image sensor of claim 1, wherein a difference between therefractive index of the isolation layer and the refractive index of thefirst and second color filters is configured such that a totalreflection critical angle at an interface between the first and secondcolor filters and the isolation layer is greater than 45 degrees.
 3. Theimage sensor of claim 1, wherein a thickness of the second color filteris smaller than a thickness of the first color filter.
 4. The imagesensor of claim 1, wherein a distance between the light incident surfaceof the first color filter and the light sensing layer is the same as adistance between the light incident surface of the second color filterand the light sensing layer.
 5. The image sensor of claim 1, furthercomprising: a transparent dielectric layer disposed on the color filterlayer; and a color separation element fixed within the transparentdielectric layer, disposed opposite the first color filter, andconfigured to transmit light in the first wavelength band to the firstcolor filter and to refract or diffract light in the second wavelengthband toward the second color filter.
 6. An image sensor comprising: alight sensing layer configured to generate an electrical signal usingincident light; a color filter layer disposed on the light sensinglayer, wherein the color filter layer comprises a first color filterconfigured to transmit light in a first wavelength band and a secondcolor filter configured to transmit light in a second wavelength band,different from the first wavelength band; an isolation layer disposedbetween the first color filter and the second color filter, wherein arefractive index of the isolation layer is lower than a refractive indexof any one of the first color filter and the second color filter; and acolor separation element that is disposed opposite the first colorfilter and configured to transmit light in the first wavelength band tothe first color filter and to refract or diffract light in the secondwavelength band, wherein the isolation layer is further disposed on alight incident surface of the first color filter and between the secondcolor filter and the light sensing layer, and wherein a surface level ofa light incident surface of the second color filter is identical to asurface level of the light incident surface of the first color filter.